Transport belt

ABSTRACT

A transport belt, in particular an endless suction belt, for conveying sheets to a press, can be driven, deflected over at least two rollers, and guided over a conveyor table. The lateral edges of the transport belt have a high degree of roughness or a structure, in order that no constant sharp edge is produced by the edges of the transport belt curving upward in the deflection region.

BACKGROUND OF THE INVENTION

Field of the Invention

The invention pertains to a transport belt, in particular a suction belt, for conveying sheets. The transport belt can be driven, deflected over at least two rollers, and guided over a conveyor table.

A transport belt of that type is described, for example, in German published patent application DE 44 13 286 A1. There, a deflection roller is arranged in the overlap region of the sheet to be aligned on front lays. The transport belt, when deflected, tends to turn up slightly at its margins or edges which are fabricated within exact tolerance limits. As a result, markings are left behind on the undersides of the sheets. In particular in the case of sheets which are coated or already printed on the underside, these markings from the transport belt have a negative impact in terms of quality, and in the worst case they result in rejects.

SUMMARY OF THE INVENTION

It is accordingly an object of the invention to provide a transport belt with a structure that overcomes the above-mentioned disadvantages of the heretofore-known devices and methods of this general type and which provides for a transport belt wherein the tendency to cause markings on the sheet is avoided, or at least reduced.

With the foregoing and other objects in view there is provided, in accordance with the invention, an improved transport belt for conveying sheets, such as an endless suction belt, configured to be driven, deflected over at least two rollers, and guided over a conveyor table. The improvement is found in the fact that the transport belt has lateral edges, or margins, formed with an edge structure.

In accordance with an added feature of the invention, the edge structure is a roughness with a laterally extending amplitude of RZ>1 millimeter.

The edge structure may have a shape described as zigzag, sinusoidal, square wave, sawtooth, and/or meandering.

With the above and other objects in view there is also provided, in accordance with the invention, a conveying table for conveying sheets to a sheet-processing machine, comprising:

a suction box;

at least two deflection rollers; and

an endless transport belt guided over said suction box and deflected about said deflection rollers, said transport belt being a suction belt with lateral edges formed with an edge structure.

It is a particular advantage of the invention that the edges of the transport belts have a high roughness or substantially a defined edge structure in a region facing the belt. As a result of this measure, marking of the transport belts on the underside of the sheets is avoided. In particular, the edges of the transport belts can be formed in the shape of a zigzag, sinusoidally, irregularly, in the shape of prongs, in the shape of sawteeth or in the shape of a meander. Alternatively, it is proposed to render the edges safe by means of a chamfer or rounding.

Other features which are considered as characteristic for the invention are set forth in the appended claims.

Although the invention is illustrated and described herein as embodied in a Transport Belt Forms, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.

The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic side view of a rotary press;

FIG. 2 is a schematic sectional view of a feed table of the printing press;

FIG. 3 is a partial plan view of a transport belt according to the invention;

FIGS. 4-8 are similar plan views showing alternative transport belt designs; and

FIGS. 9 and 10 are transverse-sectional views of a transport belt with a chamfered edge and a rounded edge, respectively.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the figures of the drawing in detail and first, particularly, to FIG. 1 thereof, there is shown a machine for processing sheets 7—here, a rotary printing press 1—with a feeder 2, at least one printing unit 3 and 4 and a delivery 6. The sheets 7 are removed from a sheet stack 8 and, separately or overlapping in imbricated relationship, are fed over a feed table 9 to the printing units 3 and 4. Each of the units 3 and 4 has a plate cylinder 11, 12 respectively. Each of the plate cylinders 11 and 12 has an apparatus 13, 14 for fixing flexible printing plates. Furthermore, an apparatus 16; 17 for semiautomatic or fully automatic printing plate change is assigned to each plate cylinder 11; 12.

The sheet stack 8 rests on a pile board or stack board 10 which can be raised under control. The removal of the sheets 7 is carried out from the top side of the sheet stack 8 by means of a so-called suction head 18 which, inter alia, has a number of lifting and dragging suckers 19, 21 for separating the sheets 7. Furthermore, blowing devices 22 for loosening the upper layers of sheets and sensors 23 for tracking the stack are provided. In order to align the sheet stack 8, in particular the upper sheets 7 on the sheet stack 8, a number of lateral and rear stops 24 is provided.

The sheets 7 arriving in the front region, facing the press, are aligned in the transport direction by means of front lays 26 and transversely with respect to the sheet transport direction by way of side lays, i.e., lateral aligning means 27. In this case, a relative movement between sheet and transport belts 29 arises, which can lead to the above-mentioned, undesirable markings. Such relative movements can also arise, for example, if the sheets are moved more quickly by another transport apparatus that is provided than by the transport belt 29.

The feed table 9 in the exemplary embodiment according to FIG. 2 is constructed as a suction belt table having a connection to a vacuum or suction source 28. At least one endless transport belt 29 wraps around the feed table 9 and has a first deflection roller 31 in the front region and has a second driven deflection roller 32 in the region facing the feed stack 8. The first deflection roller 31 is arranged at a distance a from the front lays 26 and is located in a region of an overlap length s. The transport belt 29 has suction openings which exert a suction action on the transport belt that is produced by the suction source 28 and the suction box 33. The transport belt 29 has lateral edges 34, 36 which have a coarse structure or roughness RZ>1 millimeter. In this case, it is important that the edges 34, 36 are not straight (within close tolerances). Preferred structures are illustrated in the plan views of FIGS. 3 to 8.

FIG. 3 shows irregularly shaped edges 34, 36 with a roughness RZ>1 millimeter. FIG. 4 shows a zigzag shape. The amplitude of the roughness RZ of the margin structure is indicated in FIG. 4. FIG. 5 shows a sinusoidal shape, FIG. 6 shows a pronged shape or square wave shape, FIG. 7 shows a sawtooth shape, FIG. 8 shows a meandering shape of the edges 34, 36 of the transport belt 29.

In a further alternative embodiment, the edges 34, 36 of the transport belt 29 may be provided with a chamfer 37, as illustrated in FIG. 9, or with a rounding 38, as illustrated in FIG. 10.

This application claims the priority, under 35 U.S.C. § 119, of German patent application No. 10 2004 046 293.3, filed Sep. 24, 2004; the entire disclosure of the prior application is herewith incorporated by reference. 

1. In a transport belt for conveying sheets, configured to be driven, deflected over at least two rollers, and guided over a conveyor table, the improvement which comprises: the transport belt having lateral edges formed with an edge structure.
 2. The transport belt according to claim 1 configured as an endless suction belt.
 3. The transport belt according to claim 1, wherein the edge structure is a roughness with a laterally extending amplitude of RZ>1 millimeter.
 4. The transport belt according to claim 1, wherein the edge structure is has a zigzag shape.
 5. The transport belt according to claim 1, wherein the edge structure has a sinusoidal shape.
 6. The transport belt according to claim 1, wherein the edge structure has a square wave shape.
 7. The transport belt according to claim 1, wherein the edge structure has a sawtooth shape.
 8. The transport belt according to claim 1, wherein the edge structure has a meandering shape.
 9. The transport belt according to claim 1, wherein the edges of the belt are formed with a chamfer.
 10. The transport belt according to claim 1, wherein the edges of the belt are formed with a rounding.
 11. A conveying table for conveying sheets to a sheet-processing machine, comprising: a suction box; at least two deflection rollers; and an endless transport belt guided over said suction box and deflected about said deflection rollers, said transport belt being a suction belt with lateral edges formed with an edge structure. 